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Traditional strategies for teaching clinical procedures can be inadequate so that, by the end of their training, physicians may fail to achieve competence even in basic procedural skills. Simulation training has been shown to improve procedure competencies. We developed an inexpensive simulation tool for percutaneous renal biopsy that mimics biopsy conditions in human patients in terms of kidney size, depth, tissue echogenicity and overall structural characteristics. This tool can be prepared with logistically simple approach and minimal time requirements - by inserting a porcine kidney under a turkey breast (both available from meat or grocery stores). The use of this tool for the initial renal biopsy training, as well as for maintenance of already acquired skills, has received overwhelmingly positive feedback from fellows in major adult and pediatric nephrology training programs. Future studies should establish the efficacy of this simulation training in reducing discomfort and adverse renal biopsy outcomes in human patients.
Percutaneous renal biopsy plays an essential role in the diagnosis and treatment of multiple renal disorders. Consequently, the Accreditation Council for Graduate Medical Education (ACGME) program requires that both Pediatric and Internal Medicine nephrology fellows develop competent biopsy skills for autologous and transplanted kidneys obtained through formal instruction and clinical experience.1
As an invasive procedure, percutaneous renal biopsy may be associated with increased risk for adverse, even lethal, outcomes (reviewed in 2–4). Since many procedural outcomes depend on physicians’ skills and experience, it has been suggested that the incidence of adverse renal biopsy outcomes may be increased in hospitals with training programs,5 presumably due to inadequate training. In fact, both trainees and practitioners viewed inadequate training as a significant barrier to acquiring and maintaining procedural skills.6 Unfortunately, traditional strategies for clinical teaching are often insufficient and trainees may fail to achieve competence in even basic procedural skills by the end of their training (reviewed by Gaines et al).7 An attractive solution to this problem is an invasive procedure simulation, an approach that has already been shown to effectively improve a variety of procedural skills.7 In concert with these findings, the ACGME recommends the use of simulation as one of the most desirable methods for teaching and assessing procedural skills in patient care.8 However, in the case of percutaneous renal biopsy, no simulation has been widely implemented by nephrology training programs.
We have developed an inexpensive tool for percutaneous renal biopsy simulation that also allows training in real-time ultrasound-based biopsy guidance. This tool can be prepared with a logistically simple approach and minimal time requirements by inserting a pork kidney under a turkey breast (Figure 1). We used porcine or bovine kidneys and turkey breasts purchased in local butcher shops or grocery stores.
Ultrasonographic evaluation of this renal biopsy simulation tool revealed close resemblance with human patients in terms of kidney size, depth, tissue echogenicity and overall structural characteristics (Figure 2a and 2b). Similarly, this simulation also mimicked percutaneous renal biopsy in humans by providing comparable ultrasonographic image in terms of biopsy needle guidance (Figure 2c), as well as muscle and kidney tissue resistance to passing biopsy needle. These characteristics were preserved even when the tools was used multiple times by a large number of trainees (e.g., n=14) during an entire teaching session. Feedback on this tool by novice first year fellows, as well as biopsy-proficient second year fellows and attending physicians, was overwhelmingly positive. Therefore, we incorporated this renal biopsy simulation into the core curriculum of our nephrology training programs.
Here we describe an inexpensive, logistically straightforward tool for a simulation of real-time ultrasound guided renal biopsy that mimics characteristics of this procedure in humans with respect to key radiographic and structural tissue characteristics. A possible alternative to this approach is a simulation of real-time ultrasound guided renal biopsy on minimally embalmed human cadavers.9 Although this alternative approach may more closely resemble actual biopsy procedure in humans, its use may be limited by logistical issues associated with this approach (e.g., securing cadavers for such training and transport of ultrasound imaging system between areas dedicated to patients and cadavers).
Although we found this biopsy simulation tool useful for training of pediatric and adult kidney biopsies, it does not appropriately simulate the increased depth of kidneys in some patients (e.g., in overweight adults it may exceed twice ~5 cm thickness of a large turkey breast). To improve attainment of skills required for biopsy of such deeper kidneys, we increased length of biopsy needle trajectory through turkey breast by approaching the kidney phantom with biopsy needle under more acute angle.
While renal fellows and practicing attendings in our nephrology training programs evaluated the above described renal biopsy simulation tool very positively, rigorous assessment of this phantom is needed as well as formal evaluation to determine effectiveness of such simulation training in reducing adverse renal biopsy outcomes and patients’ subjective experiences with this procedure.
This simulation tool can be prepared with logistically simple approach and minimal time requirements. The cost of required material (turkey breast and two pork kidneys) at local butcher shops or grocery stores was approximately $20. Since turkey breast thickness limits the depth of kidney phantom, we purchased the largest available turkey breasts. We prepared this simulation model by inserting a frozen kidney into a hand-made pocket under each side of thawed turkey breast (Figure 1). To prevent air-trapping around the kidney and consequent ultrasonographic artifacts, pocket formation and kidney insertion were performed under water seal. We created the water seal by placing the breast into a large plastic bag (that was inserted for better stability into a large box) and filling it with water. When both kidneys were successfully placed under each side of the breast, excess of water was descanted and the plastic bag tightly secured near the opening in the breast that was used for the kidney insertion. Finally, we placed the bag with the breast into a slightly smaller box to allow positioning of the inserted kidneys into nearly horizontal position. This box was lined up with another plastic bag to prevent potential fluid leakage. When completed, this simulation tool was stored for one day at 4°C to allow the kidneys to completely melt. We handled the turkey, pork or sheep tissues in latex or nitrile gloves. In case of accidental contact, hands were scrubbed vigorously with soap for at least 20 seconds. All surfaces that were in contact with these tissues were disinfected.
After initial review of the basic principles of ultrasonographic guidance and renal biopsy procedures, the fellows observed an experienced operator perform several real-time ultrasound-guided biopsies using the simulation tool. After that, individual fellows practiced real-time ultrasound-guided renal biopsy procedure repeatedly until they attained reasonable accuracy and gained confidence. Guidance and feedback were provided immediately by an experienced operator.
This simulation was performed using standard ultrasound imaging instruments (e.g., Diagnostic ultrasound system Aplio Model SSA-770A; Toshiba Medical Systems Corporation, Tochigi-Ken, Japan). Biopsies were performed with semi-automatic needles (e.g., Bard MaxCore Instrument with 18G, 20 cm long needle, 22 mm through; C. R. Bard, Inc., Murray Hill, NJ).
This work was supported in part by the UAB-USCD O’Brien Center 1P30 DK079337 (MM) and by the Department of Defense and the National Institutes of Health T32DK007695 (JJB).
The authors have no conflict of interest to disclose.